SI FANG Turbine Reciprocating Pneumatic Ultrasound Grinder Micro Pneumatic Air Pencil Die Grinder Kit for Mould Metal Lapping Filing Grinding Buffing Polishing Sanding Tools

I am really impressed by this ultrasonic air-pencil grinder. I use it to relieve (open up) dimensions on slots and holes in laser-sintered components in 316L stainless steel in very fine increments of 0.0001” to 0.001” to make passage for inter-locking parts needing press-fit to slip-fit clearances. I much prefer this air-pencil grinder to using a milling machine to post-process my 316L SS parts as milling tends to heat and work-harden the surfaces. When using this air-pencil grinder, my 316L SS parts stay cool to the touch and never seem to even get warm. Though the product info says this air-pencil grinder needs around 2.9 cfm @ 90 PSI, I like to run it from a DeWalt pancake compressor that is rated to deliver 2.6 cfm @ 90 PSI. I can operate this air-pencil grinder at max “output” for about 10 minutes before the air pressure drops too low. With the motor on the single-stage compressor running constantly, the air pressure is sufficient to operate this air-pencil grinder at max output continually. I just wear ear-muffs to keep the constant loud noise from the compressor motor nearby from irritating and damaging my hearing. The reciprocating motion of the motor head is a forward-and backward oscillation in a slightly circular motion. This means that depending on the contours of what you are trying to grind, it is best to experiment with flipping the grind-head, bit or file that you are using to determine which oscillation loci gives the least amount of chatter. In other words, if you’re not getting smooth, grind action, just rotate the grinding head by 180 degrees. You don’t need to apply a lot of hand pressure. Light, even strokes give the best results. With flat-file heads, grinding metal at an angle is preferable to holding the grind head perpendicular to the surface being filed or ground. Too much hand pressure on a jack-hammer trajectory causes chatter and can chip your flat-file heads. When opening the diameter of thru-holes, I get the best, fastest results by holding both the hole and a round-file grinding head passing through it, vertically, and rotating the round-file head around the perimeter of the hole instead of pushing it back-and-forth along the bore axis of the hole. If you’re not getting the amount of material removal you desire, especially when grinding hard metals, the trick is not to increase the air-pressure from your compressor, but to lower the grit size of your grind heads to use more coarse abrasive. Be careful, as once you drop below #120 diamond grit, even hardened steel can come off much faster than expected — and it is way easier to remove metal than to replace it! I use light oil for lubricating jack-knifes, such as Swiss Army Knives, to lubricate this air-pencil. A few drops with a needle applicator into the [brass] air inlet nozzle at the rear of the air-pencil grinder before every use will keep things running smoothly. I suspect a lot of tool breakages that are cited in the comments are because users are not lubricating their air-pencil grinders frequently enough, are turning up the air pressure from their compressors past 90 psi, and are forcing their grind-heads into their parts like they are drilling them. The adapter for round-shaft grind-heads is installed as the factory default. A clamp adapter for holding flat-file heads is included, and is notched for smaller-diameter (e.g. less than 3 mm dia) round-file heads. Do not try to install the clamp adapter in place of the default adapter — the clamp adapter has a round stem slides into the default adapter. NOTE; when you are using the included hex wrench to tighten or loosen any of the adapters or tool holders, do not hold and torque against the body of the air-pencil grinder. Hold the adapters themselves. I suspect this is another cause for tool breakages, where users are using the body of the air-pencil grinder like a wrench handle. Don’t do this! There are reviewers who have cited that the air-hose coupler included in the kit is not the U.S. standard interface. The one that came with mine is compatible with and correct for all my U.S. standard air compressor equipment. The kit comes with a set of file head grinders in duplicate. The redundancy is nice as the ultrasonic oscillations can wear off even diamond grit in a short time. I use all variety of parallel round files with this air-pencil grinder after cutting their shanks (handles) to shorter lengths. I even use the grinding bits for sharpening chainsaw links in this air-pencil grinder, and the ones with the more coarse grit will trim away even hard steel with surprising speed. For $58, this air-pencil grinder is a great value that does the job of equipment priced 10X greater. At its very affordable price, I would just buy another one if this one breaks. However, with the right maintenance and care, as described above, I suspect this air-pencil grinder will last a long time. I’m really impressed with this air-pencil grinder. It’s been immensely useful to me right out of the box as a fine grinding tool. Used properly, it does in minutes on hard steel what would take days for me to grind manually / by hand. Remember that it is an air-pencil grinder and not an air-chisel or bench grinder and it will serve you well.

This is what I've needed for quite some time. The short stroke is great for detailed work and the variable rate is useful as well. The only downside is the spacing of the slot is just a bit too wide to hold a blade for cutting rather than sanding. As a sander it is amazing!

Great for deburring detail cuts in aluminum sheet parts. Makes a boring miserable job somewhat more tolerable. Note: the air coupler provided won't fit any coupling you can easily buy but it's a straightforward matter to replace the provided air hose with a standard airbrush supply hose. You can buy them here on Amazon for $10 or less.

I love this thing. This thing is good for small material working it revs up like a turbine engine and goes. But be careful it requires high CFM flow

It is quiet and well made in Taiwan. It holds round and flat shanks (with adapter). It vibrates really fast and you can control the speed of vibration